I was a little disappointed by the lack of explanation on how light refracts. It references Snell's law and mentions how light travels slower in water, but it did not go into how it's an effect of parts of the wavefront changing velocity at slightly different times as a result of the light entering the medium at an angle (or at least that being a simple way of understanding refraction.)

However, it was cool to see them reference "Do dogs know calculus?" I actually saw Pennings give a presentation on it in high school because my calc teacher was one of his students. He started out the talk by telling us that his dog knew calculus. He then proceeded to ask his dog the derivative of x^3. The dog did nothing, and he told us that dogs don't know calculus.